Circuit for an electro-eroding machine for the control of the relative movement between at least one electrode and at least one workpiece

ABSTRACT

This invention relates to a circuit for an electro-eroding machine for the control of the relative movement between at least one electrode and at least one workpiece by virtue of data stored on an information carrier which relative movement contains at least one length of curve defined by the data and which data are corrected in consideration of the thickness of the electrode, the width of the operating gap, the erosive condition in the operating gap and which are supplied to at least one advancing device for the electrode and/or the workpiece as control signals generated in a computing unit by means of an interpolation process.

United States Patent [191 Ullmann et al.

[ 51 May 1,1973

[ CIRCUIT FOR AN ELECTRO-ERODING MACHINE FOR THE CONTROL OF THE RELATIVEMOVEMENT BETWEEN AT LEAST ONE ELECTRODE AND AT LEAST ONE WORKPIECE [75]Inventors: Werner Ullmann, Locarno-Muralto;

Laszlo Rabian, Locarno-Monti; Silvano Mattei, Locarno-Solduno; ArnoSieg, Locarno; Peter Suter, Locarno; Costantino Tadini, Locarno, all ofSwitzerland; Rudolf Panschow, Hannover, Germany; Volker Suhr, Neustadta./Ruebenberge, Germany; Wolfgang Meyer, Hannover, Germany [73]Assignees Agie, A.G. fur industrielle Elektronik, Losone-Lorcarno,Switzerland 22 Filed: July 1,1971 21 Appl. No.1 158,721

[52] US. Cl. ..2l9/69 V [51] Int. Cl. .....B23p 1/12 [58] Field ofSearch ..2l9/69 C, 69 G, 69 P,

219/69 R, 69 S, 69 V [56] References Cited UNITED STATES PATENTS2,974,216 3/1961 lhoue ..219/69 V 3,591,761 7/1971 Bederman et al...3,610,864 10/1971 Kholodnov ..219/69 V Primary ExaminerR. F. StaublyAtl0rneyL. Gaylord Hulbert et al.

[ ABSTRACT This invention relates to a circuit for an electro-erodingmachine for the control of the relative movement between at least oneelectrode and at least one workpiece by virtue of data stored on aninformation carrier which relative movement contains at least one lengthof curve defined by the data and which data are corrected inconsideration of the thickness of the electrode, the width of theoperating gap, the erosive condition in the operating gap and which aresupplied to at least one advancing device for the electrode and/or theworkpiece as control signals generated in a computing unit by means ofan interpolation process.

' 13 Claims, 7 Drawing Figures Patented May 1,1973 7 4 Sheets-Sheet 1Fig. 1

, l ,5! K 4 11.x"

INVENTOR S WERNER ULLMANN LASZLO RABIAN SILVANO MATTEI ARNO SIEG .PETERSUTER- GOSTANTINO TADINI RUDOLF PANSCHOW VOLKER SUHR WOLF GANG MEYE RATTQRNEYS Patented: May 1, 197 3 Q 3,731,045

4 Sheets-Sheet L 1/7,, I I Fig.5

} 1 ,15 r" ;'//7, 114 ge.

lNVE-NTORS ATTORNEYS CIRCUIT FOR AN ELECTRO-ERODING MACHINE FOR THECONTROL OF THE RELATIVE MOVEMENT BETWEEN AT LEAST ONE ELECTRODE AND ATLEAST ONE WORKPIECE In 'a known programme-controlled electro-erodingmachine the relative movement between a shaped electrode ora wireelectrode and a workpiece is controlled by an electrical circuit byvirtue of the data which are stored in a punched tape so that thedesired workpiece contour can be produced. Practice has revealed that 1complex components must be incorporated in the electronic circuit forcomplex curves in the workpiece con-' tour. Complex curves aresuperpositions of simple 7 curves. This resulted in great expenditurefor the electronic control as compared to that for the electro-erodingmachine, which is undesirable. In order to keep expenditure for theelectronic control at a reasonable level one has limited oneself tosimple curves of the workpiece contour between the electrode and theworkpiece. Simple curves are straight lines, circles, ellipses,parabolas and the like which must be painfully combined into a workpiececontour, only an approximation of the simple curves to the realworkpiece contour being in many cases obtained. The desired reduc tionof expenditure for the electronic control was secured by dispensing withthe possibilities of application which can be readily achieved by theelectro-eroding machine proper. There is thus a bottleneck in theelectronic control. 7

In order to provide a reasonable proportion between the expenditure forthe electronic control and the expenditure for the electro-erodingmachine while all imaginable curves of the workpiece contour are eroded,control system have been evolved which are disclosed in the Swiss Pat.applications Nos. 9594/70, BE 13 886 and- 10123/70, BE 13 887 of thesame applicants. These control systems are characterized by their simplebasic conception on the construction block principle and are designedfor special problems of electric erosion, particular weight beingattached to the simplicity of programming the curve.

The present invention relates to a component which can be incorporatedin such control systems. The component according to this invention maybe used in the control of a shaped electrode and/or a wire electrode.

The invention is characterized by an indexing unit comprising:

a memory to receive the data for the angle of rotation a, by which anglethe system of co-ordinates of the curve portion is to be rotated, thesaid data being stored in theinformation carrier;

a computing circuitto receive the corrected data of the curvelengthian'd the data of the angle of rotation a supplied by the memory,which computing circuit calculates, in a multiplication circuit and anaddition and subtraction circuit, the new data of the curve portionrotated by. the said angle a and supplies them as signals to a: circuitarranged downstream thereof, and

the control circuit designed as a memory or computing unit.

Embodiments of the invention are explained in greater detail withreference to the drawings in which FIG. 1 is an advancing device inperspectivezview to illustrate the mode of operation of the invention;

FIG. 2 is a box-type representation of the complete control circuit forthe control of the relative movement between the workpiece and theelectrode;

FIG. 3 is a box-type representation of an embodiment of the arrangementof the indexing unit in the control circuit according to FIG. 2;

FIG. 4 is box-type view of a further embodiment of the arrangement ofthe indexing unit in the control circuit according to FIG. 2; 0

FIG. 5 is a box-type representation'of another embodiment ofthearrangement of the indexing unit in the control circuit according toFIG. 2;

FIG. 6 is an embodiment of the computing circuit of the indexing unit,and

FIG. 7 shows a workpiece shape produced by the indexing unitincorporated in the control circuit according to FIG. 2.

The advancing device of FIG. 1 is only an example of variousembodiments. With this advancing device a wire electrode is employed forthe electro-erosive cutting of the workpiece contour. With a somewhatdifferently designed advancing device, a shaped electrode for erodingrecesses, such as engravings with particularly shaped recesses andcurves, can be employed. The following explanations, which relate to awire electrode, therefore apply to a shaped electrode in the samemanner. The advancing device shown in FIG. 1, which is arranged in aneroding machine in the manner known, substantially consists of the twocross-tables l5, 16; Each cross-table can be displaced on the twoco-ordinates x and y. Each cross-table consists of the two mobileportions 17, 18, 19, 20. Attached to each mobile portion is a drivingmotor 11, 14, 21, 22. The driving motors are connected to thecorrespondingly designated outlets of the control circuit shown in FIG.2. The holding device 3 for the wire electrode 36 consists of the twowire guides 31, 32. One wire guide 31 is attached to the mobile portion17 of the cross-table 16 and the other wire guide 32 is attached'to themobile portion 18 of the cross-table 15. The wire electrode 36 consistsof a copper wire of e.g. one to three millimeters diameter which iswound on a supply spool (not shown). In erosive operation the wireelectrode is wound, from the supply spool, on another spool (not shown)so that the wire electrode is moved at a constant velocity via guiderollers merely indicated in FIG. 1. Located between the wire guides 31,32 is the workpiece 33 which is only indicated for greater clarity. Theworkpiece 33 is attached to a firm support and placed in the container34 which is located on the table of the eroding machine. Arranged in thesaid container 34 is the dielectric medium necessary for the performanceof erosion. The wire electrode 36 is taut between the two pins 37 whichare attached to the wire guides 31, 32. These pins may be replaced byother means for stretching the wire electrode, such as funnel-typemeans. In FIG. 1 the wire electrode is so tensioned between the pins 37of the wire guides 31, 32 that it forms a right angle with the surfaceof the workpiece. If the two cross-tables 15, 16 are moved in parallelon the x and y-co-ordinate, the wire electrode 36 maintains the angularposition relative to the surface of the workpiece 33 shown in FIG. I anderodes contours or shapes plied to an information carrier and areconverted into control signals, via the control circuit according toFIG. 2, for the driving motors 11, 14, 21, 22 of the two crosstables 15,16. This produces contours or shapes having a straight cut face. If onewire guide is displaced relatively to the other, the wire electrode 36forms an angle [3 with the surface of the workpiece 33. The angle B isin that case smaller than 90. This oblique position of the wireelectrode relative to the surface of the workpiece enables conicalcontours or figures to be produced from the workpiece 33. The mobileportions 17, 19, 18, 20 of the two cross-tables l5, 16 move similarly inparallel when the conical contours are cut. This will later be discussedin greater detail with reference to FIG. 2. In FIG. 1 an arrow zindicates that the wire guide 31 can be moved on the z-co-ordinate. Thismovement may be effected either manually or by a further driving motor(not shown). The displacement on the z-co-ordinate is necessary if thedistance between the two wire guides 31, 32 must be adjusted to thethickness of the workpiece 33 being processed. As is well known, thewire guide 31 is above and the wire guide 32 is underneath theworkpiece. The displacement of the wire guide 31 in the z-directionchanges the angle [3 in conical cutting.

The circuit according to FIG. 2 controls the movements of the wireelectrode 36 just described by virtue of data stored in an informationcarrier. The information carrier may be a punched tape, punched card ora magnetic tape. Recorded in the information carrier are thecharacteristic points of the path which the wire electrode 36 is calledupon to travel in the workpiece 33. The characteristic points are 'thestarting and end points of a curve length, which may be a straight line,a circle, an ellipsis, a parabola, an involute or a cycloid. Theinvoluteis formed, as is well known, by the superposition of the straightmovement and a rotary movementQThe cycloid is formed, as is well known,by the superposition of a circular movement and a rotary movement.

The characteristic data of the information carrier are given by theinput 100 to the control circuit 2. This input may be acharacter-reader, punched-tape reader, punched-card reader,magnetic-tape device or picture scanner employing a Braun tube. This isdetermined by which information carrier could be most suitable for acertain assignment given to erosion. For the following description ofthe control circuit according to FIG. 2 it is assumed that theinformation carrier is a punched tape. The punched-tape reader 100supplies the data to the buffer memory 102. A code converter 103 isarranged downstream of the buffer memory 102. The code converter 103must convert the data of the punched tape. If some other informationcarrier is employed, the code converter 103 can be dispensed with. Theconverted data then pass into the correcting computing unit 104 whichconverts the characteristic points into corresponding characteristicpoints of the path of the axis of the wire electrode 36. In this processthe width of the operating gap 111 is considered. The characteristicpoints of the workpiece contour supplied to the information carrierdiffer from the path curve on which the axis of the wire electrode 36moves by one half of the diameter of the wire electrode and the width ofthe working gap 111. If a shaped electrode is employed for eroding orrecesses, the thickness of the shaped electrode and the width of theoperating gap must be considered. The thickness of the shaped electrodeis understood to be its spatial dimensions relative to the center pointof the electrode holder. The correcting computing unit 104 to this endreceives, from the manual input 107, the values for the diameter of thewire electrode and for the width of the operating gap. If desired, thedata relating to the wire diameter and, respectively, the thickness ofthe shaped electrode and the gap width may be stored on the informationcarrier as additional information so that the manual input 107 is notrequired. By means of the manual input 107 the additional informationfrom the punched tape can naturally be corrected. The output signalssupplied by the punched tape which define the path curve of the wireelectrode 36 are supplied to the interpolator and the indexing unit 117.The points 0 and d are interconnected as shown in FIG. 2. These pointsare separated if the wire electrode 36 is called upon to cut conically.The mode of operation of the indexing unit 117 will be described laterso that only the general control will be described. The interpolator 105converts, by virtue of the output signals representing thecharacteristic points, the complete path curve according to apredetermined programme. For this purpose, either the search-stepprocess, which is also designated as an iteration interpolation, or theDDA Digital Differential Analyzerand, respectively, approximationprocess is employed. The control signals from the interpolator 105,which indicate the points of the path curve located between thecharacteristic points thereof, pass to the two cross-tables l5, 16 ofwhich the driving motors l l, 14, 21, 22 displace the moving parts 17,18, 19, 20 in the desired manner. The wire electrode 36 describes thepath curve and cuts the curve portion from the workpiece 33 as per thedata supplied by the punched-tape reader 100. It is here assumed thatthe wire electrode and the surface of the workpiece 33 enclose a rightangle B. Conical cutting will be explained later.

The mode of operation of the part component 117 will now be described.Reference is here made to the workpiece contour of FIG. 7. The workpiececontour 340 of FIG. 7 is composed of several congruent curve lengths.The congruent curve lengths differ from one another only by theirrelative position. So far the data of the characteristic points of eachcongruent curve length have had to be stored in the information carrier.This complicated programming is eliminated by the indexing unit 117. Theindexing unit 117 rotates the system of co-ordinates by the desiredangle so that a congruent curve length, e.g. from point 341 to the point342 of the workpiece contour 340 in FIG. 7, must be stored in theinformation carrier. The x, y system of co-ordinates can be rotated asmany times as desired. The indexing unit 117 for this purpose onlyrequires the angle of rotation B from the information carrier. Uponrotation of the system of co-ordinates the same data of the curve lengthpreviously eroded are used to erode the subsequent curve length frompoint 342 to point 343 in FIG. 7. When the wire electrode has reachedthe point 343, the system of co-ordinatcs is again rotated. The samecharacteristic data as used for the preceding congruent curve lengthsare used for eroding the congruent curve length from the point 343 tothe point 341.

Prior to disclosing the indexing unit 117 in greater detail, theindividual components of the general circuit of FIG. 2 will now brieflybe explained.

If the wire electrode 36 is to cut conically, a conicity computing unit118 is provided in the circuit according to FIG. 2, the said unitcalculating the characteristic points of the curve length inconsideration of the conicity angle [3, of the distance between the twopins 37 on the wire guides 31, 32 and the distance of a pin 37 from asurface of the workpiece 33. The conicity computing unit 118 is arrangedbetween the part component 1 17 and the interpolator 105 for thecross-table in the principal connecting line. The connection between thepoints c and d is suppressed in this case. The devices and connectionsrequired for conical cutting are shown in broken lines in FIG. 2. Theconicity computing unit 118 supplies its output signals to theinterpolator 105 for the cross-table 15 already described, and to theinterpolator 119 which controls the driving motors 21, 22 of thecross-table 16. In this case, the dot-dash connecting line between theinlet of the cross-table l5 and the inlet of the cross-table 16 iseliminated. The data for the conicity computing unit 118, such as angle,8, distance between the pins 37 of the two wire guides 31, 32, distancebetween pin 37 of the lower wire guide 32 and a theoretical point ofintersection at the lower face of the workpiece 33, may be supplied bymanual input12l or by additional data supplied by the informationcarrier to the conicity computing unit 118. The manual input 121 maynaturally complement and/or correct the additional data supplied by theinformation carrier. In conical cutting, the wire electrode describes,e.g. on the upper face of the workpiece 33, a path curve which isequidistantly spaced from the path curve on the lower face of theworkpiece. The manual input 109 also enables the driving motors 11, 14,21 22 of the cross-tables 15, 16 to be controlled which may be necessaryin various cases. Each interpolator 105, 119 is equipped with a returnmemory 108, 122. These return memories are provided so that, in theevent of trouble in the operating gap 111, the wire electrode 36 canreturn along the same curve length. Stored in the return memory inparallel with each associated interpolator are the characteristic datasupplied by the correcting computing unit 104 (for straight cutting withthe wire electrode 36) or by the conicity computing unit 118 (forconical cutting with the wire electrode). The monitoring device 110, ifit detects trouble or a short-circuit in the operating gap 111, suppliesa trouble signal, to the interpolator 105 (in straight cutting.) or tothe two interpolators 1 05, 119 (in conical cutting) so that the controlsignals supplied to the driving motors 11, 14, 21, 22 of the twocross-tables 15, 16 are stopped. A further signal from the monitoringdevice 110 reaches the return memories 108, 122 so that they supply thestored characteristic data-of the curve length just travelled by thewire electrode 36 to the interpolators. The latter interpolate thecharacteristic data in inverse order and supply the control signals tothe driving motors of the two cross-tables. The wire electrode 36returns by the curve length just travelled until the trouble'in the xoperating gap 111 has been eliminated. In the event that the trouble inthe operating gap 111 is not yet remedied, the wire electrode will alsoreturn over the previous curve length. The return memories 108, 122 areso designed that they can store several curves. As soon as the troublein the working gap 111 is remedied, the monitoring device 110 gives aclear signal to the interpolators and return memories. The wireelectrode 36 is then advanced along the same curve lengths until itreaches the position in which the trouble or the short-circuit in theoperating gap 1 11 has occurred. Subsequently, the normal erodingprocess for the cutting of the workpiece contour begins. With the manualinput 115 data relating to the desired roughness of the cut faces of theworkpiece contour, the cutting velocity of the wire electrode and thewidth of the operating gap can be supplied to the monitoring device 110.

For the purpose of controlling the processes in the circuit of FIG. 2 sofar described, the computing clocking generator 113 is provided. Forreasons of simplification, the lines of influence between the saidgenerator 113 and the individual components are not shown. The clockinggenerator receives, from the punched tape reader 100 via the buffermemory 102, the data important for control, such as positioning of wireelectrode 36 at the beginning of cut in workpiece, start of programme,end of programme", interruption and data relating to the type ofinterpolation etc. These data may be complemented by the manual input112. FIG. 2 shows a connecting line between the clocking generator113and box 114. Box 114 sympolically shows the erosion generator and adevice for controlling the flushingconditions of the dielectric mediumin the operating gap 111. Of the many lines of influence of the clockinggenerator 113 to the various components, only the control line to box114 is shown. This is designed to indicate that the erosion generatorand the device for the dielectric medium can be controlled by thepunched tape via the reading device 100and the bueffer memory.

A more detailed description will now be given of the control device 1 16which is connected to a further outlet of the buffer memory 102. Thecontrol device 1 16 is supplied, by the buffer memory 102, withadditional information which is stored in the punched tape. Suchadditional information may be:

a. data for the correcting computing unit 104 e.g. the diameter of thewire electrode 36, width of the operating gap 111;

. data for the indexing unit 117, e.g. the angle a, by which the systemof co-ordin'ates of a congruent curve length is to be rotated;

c. data for the conicity computing unit 118, e.g. conicity angle B,distance of the pins 37 of the two wire guides 31, 32 and distance ofthe pin 37 of the lower wire guide 32 from the theoretical point ofintersection which. as is well known, is located on the lower face ofthe workpiece 33;

. date for the monitoring device 110, e.g. roughness of the cut faceeroded in the workpiece 33 by the wire electrode 36, cutting velocity ofthe wire electrode 36, width of the operating gap 1 1 l;

e. data for the control of the electrical parameters for the erosiongenerator 114, e.g. current, voltage, repetitive frequency, width,interval of impulses and/or double impulses and, respectively, ignitionimpulses, and

f. data for the adjustment or modification of flushing conditions of thedielectric medium to the device Such additional information from thepunched tape may be corrected, if necessary, by the manual inputs 107,115, 121.

The divisional component 117 will now be described with reference toFIGS. 3, 4, 5, 6 and 7. As previously stated, this component is designedto simplify the programming of congruent curve lengths. A cut shapeconsisting of several congruent curve lengths is shown in FIG. 7.Further examples of congruent curve lengths are found in gears. A toothof a gear constitutes a congruent curve length. So far each individualcongruent curve length has had to be individually programmed in thepunched tape. With the aid of the electronic indexing unit 117 only asingle congruent curve length need be programmed in the punched tape. Tothis end, only the angle a which, as previously stated, indicates therotation of the system of co-ordinates need be supplied,

by the punched tape reading device 100 via the buffer memory 102 and theswitching device116, to the electronic indexing unit 117. The angle amay be stored in the punched tape either as cos a and as sin a (FIGS. 3and 4) or as a (FIG. 5) and so be supplied to the indexing units 117.The rotatory co-ordinate transformation which is effected is theindexing unit 1 17 in accordance with the equations Ax'=Axcosa-AysinaAy'=Axsina+Aycosa will be described with reference to the example shownin FIG. 7 with the arrangement of the indexing unit of FIG. 3. It isassumed that no conical cut configurations are to be produced.

The components of FIG. 2 indicated in broken lines are inoperative andthe points c and d (FIGS. 2 and 3) are interconnected. The congruentcurve length of the workpiece contour 340 from point 341 to point 342and the angle of rotation at are programmed in the punched tape. Thecharacteristic data of the congruent curve length pass, viathe punchedtape reader 100, the buffer memory 102, the code converter 103 and thecorrecting computing unit 104, to the interpolator 105 and, in paralleltherewith, to the computing circuit 117,. The computing circuit willlater be described in .detail with reference to FIG. 6. In thearrangement of the indexing unit as per FIG. 3, the angle of rotation ais stored in the punched tape as sina and cos a. These trigonometricalangular data pass, via a punched tape reader 100, the buffer memory 102and the switching device 116, to a memory 117 of the indexing unit 117.The memory 117,, passes these values on to the computing circuit 117,.The computing circuit comprises four inlet memories for the values A x,A y (characteristic points of the congruent curve length), sina, cos at(angle of rotation at). The interpolator 105 interpolates thecharacteristic data of the congruent curve length form the point 341 tothe point 342 and supplies the appropriate control signals to thedriving motors 11, 14, 21, 22 of the cross-tables 15, 16. It is herepointed out that, with a view to simplifying the description of the modeof operation of the indexing unit 117, it is assumed that the wireelectrode 36 is not called upon to produce conical cut configurations.Ac-

cordingly, the conicity computing unit 118 indicated in broken lines inFIG. 2 is not connected at the points 0 and d. If the conicity computingunit were to be used,

the connection between the points c and d would be broken and theconicity computing unit 118 with its in terpolator 119 and return memory122 would be switched on so that the interpolator 119 could control thedriving motors 21, 22 of the cross-table 16. We now revert to theassumption that the conicity computing unit 118 is not on and that theinterpolator supplies control signals to the driving motors of the twocrosstables 15, 16. While the interpolator 105 controls the drivingmotors 11, 14, 21, 22 of the cross-tables 15, 16 so that the wireelectrode 36 can erode the congruent curve length from point 341 topoint 342, the computing circuit 117, calculates, in a multiplicationcircuit, addition circuit and substraction circuit, the increments ofthe subsequent curve length from point 342 to point 343 which has beenrotated by the angle a of e.g. 120. The computing circuit 117, proceedsin accordance with the two equations previously given. In theseequations, the values A x, A y represent the characteristic data of thefirst congruent curve length from point 341 to point 342 andthe values Ax, A y the values of the subsequent curve length, which has been rotatedby the angle a of e.g. 120, from the point 342 to the point 343. Thevalues A x', A y are supplied to the memory 117,. When the wireelectrode 36 has reached the point 342, the interpolator 105 calls, fromthe memory 117, according to FIG. 2, for the values for the curve lengthwhich the wire electrode is calles upon to travel from the point 342 tothe point 343. At the same time these values are supplied to the secondinlet of the computing circuit 117, in which the congruent curve lengthis calculated which the wire electrode 36 is to travel from point 343 topoint 341. The computing circuit stores the newly calculated values inthe memory 117, in the place of the old values already called for by theinterpolator 105. The rotation of the system of co-ordinates "and,respectively, a congruent curve length is so often calculated by thecomputing circuit 117, as has been indicated when the first angle datawere given. For the workpiece contour 340 of FIG. 7 two angularrotations of the system of co-ordinates x, y and, respectively, thecongruent curve length by 120 has been given in the first angleindication. In the production of a gear which obviously consists ofsubstantially more numerous congruent curve lengths or teeth, therotation of the congruent curve length, i.e. of the tooth and,respectively, the system of co-ordinates, must be effected much morefrequently. If the conicity computing unit 118 (FIG. 2) is provided,conical gears, e.g. befel gears or conical cut configurations ortoolcontours can be cut from the workpiece 33 by means of the wireelectrode 36. The arrangement of the electronic indexing unit 117 as perFIG. 3 consists substantially of a closed control circuit between thecomputing circuit 117,, the memory 117 so that the angle a and theindication as to how many times the angle a is to be rotated must berotated in the punched tape.

In the arrangement of the indexing unit according to FIG. 4, eachangular rotation must be individually stored in the punched tape. Aftereach angle data, the characteristic data of the congruent curve lengthare supplied, by the punched tape, to the computing circuit 117,. Tothis end, a punched tape reader 100 may be employed which again readsthe characteristic data of the previous congruent curve length ininverse order and supplies them to the computing circuit 117,. A secondpunched tape may also be employed which, via a second punched tapereader, periodically reads the characteristic data of the congruentcurve length as soon as the first punched tape and, respectively,principal punched card has supplied the desired angular rotation to thecomputing circuit 117,. The second punched tape or auxiliary punchedtape may be A designed as an endless tape. The mode of operation ofthese two different punched tape programmes is similar. According to thearrangement shown in FIG. 4 the characteristic data are first suppliedby the punched tape, via the punched tape reader 100, the buffer memory102, the code converter 103 and the correcting computing unit 104, tothe interpolator 1 and the computing circuit 117,. In this embodiment itis again assumed that the interpolator 105 supplies the driving motors11, 14, 21, 22 of the cross-tables 15, 16 with control signals. Theconicity computing unit 118, the interpolator 119, the return memory 122and the manual input 121 shown in broken lines in FIG. 2 are notavailable so that the connecting line between the points 0 and d passesthrough as shown in FIGS. 2 and 4. While the interpolator 105 controlsthe wire electrode 36 for the erosion of the congruent curve length(points 341, 342 of FIG. 7), the values sin a and cos a are suppliedbythe punched tape, via the punched tape reader 100, the buffer memory102, the switching device 116 and the memory 117 to the computingcircuit 117,. The computing circuit 117, then accurately calculates, asdescribed with reference to FIG. 3, from the characteristic data Ax andAy of the first congruent curve length and from the values sina andcosa, the characteristic data A x and A y of the second congruent curvelength (points 342 and 343 in FIG. -7). When the wire electrode 36 hasreached the point 342 of the workpiece contour 340 in FIG. 7, the valuesA x and A y pass into the interpolator 105 so that the second congruentcurve length can be cut by the wire electrode. During that time thepunched tape supplies the values for the second angular rotation sin andcos 201 as well as the characteristic data of the first congruent curvelength to the computing circuit 117,. The repetition of the data of thefirst curve length is effected either by an inversely reading punchedtape reader 100 or by a second punched tape reader with an auxiliarypunched tape. In the latter case, the data for the second angularrotation are programmed in the principal punched tape. Thecharacteristic data of the first congruent curve length pass, via thepath previously mentioned (buffer memory 102, code converter 103,correcting computing unit 104), to the computing circuit 117 The valuesfor the second angular rotation pass, via the path previously described(buffer memory 102, switching device 116 to the computing circuit 117,.The computing circuit calculates, in the manner previously described,the characteristic data for the third curve length (points 343, 341 inFIG. 7). When the wire electrode 36 has reached the point 343, the newvalues for the third congruent curve length, which have in the meantimebeen stored in the computingcircuit 117,, are supplied to theinterpolator which controls the wire electrode 36 for the erosion of thethird congruent curve length. In order to keep down the programmingexpenditure for the values sina and cos a in the punched tape, the anglea can be directly stored in the punched tape instead of these values. Inthat case, the punched tape must contain additional information as tohow many times the angle must be rotated. In the arrangement of theindexing unit 117 as per FIG. 5 an interpolator 117 is additionallyprovided between the switching device 116, which as is well knowntransmits the data relating to the angle of rotation of the congruentcurve length and, respectively, the system of co-ordinates, to thememory 117;, of the indexing unit 117. This interpolator determines,from the angle indication on the trigonometrical values sina cos a andsupplies them to the memory 117;,. The arrangement of the indexing unit117 according to FIG. 5 works in a manner similar to that of thearrangements of FIGS. 3 and 4 and is therefore not described in greaterdetail. In order to simplify the arrangement of FIG. 5, the interpolator117, mayreadily be replaced by the interpolator 105 or 119. In that caseit must only be ensured that the interpolator 105 or 119 which generatesthe control signals for the driving motors of the two cross-tables 15,16 is used for the internal determination of sina, cos a during the timethat it supplies no control signals to the driving motors of the twocross-tables. It is easily possible for the time spacing of theindividual control signals coming from the interpolator 105 or 1 19 tosuffice so that it can in the meanvalues are meanwhile stored. Thecomputing sequence 1 now described in more detail with reference to FIG.6 is given by the two equations previously recited. Two of these valuesat a time are selected by the selective circuit ll7 and multiplied inthe multiplication circuit 117, The multiplied values A x, sina, A 1,cos a, A y, sina, A y, cos a are supplied to the distributor circuit 117and distributed to the intermediate memories 117, 117 117 117 Theseintermediate results are supplied, by a second selective circuit 117, toa switchable addition subtraction circuit 117, in such a manner that thefinal result is obtained. The second distributor circuit 117, passesthis final result to the two output memories 117 1 17 From these twooutput memories the interpolator 105 or the conicity computing unit 118(FIG. 2) enquires the characteristic data for the congruent curve lengthwhich is to be rotated by the angle a. The computing circuit 117 of FIG.6 can naturally be simplified by utilizingthe various components theredescribed several times in their mode of operation. It is thus possiblesubstantially to lower the expenditure for memories.

In conclusion it is pointed out that the indexing unit 117 is notlimited to the advancing device 3 of FIG. 1 with two cross-tables 15, 16but is employed also in an advancing device which has a cross-table anda rotary table for the relative movement of the wire electrode 36 andthe workpiece 33 on carthesian co-ordinates and/or on polarco-ordinates.

What is claimed is:

l. A circuit for an electro-eroding machine for the control of therelative movement between at least one electrode and at least oneworkpiece by virtue of data stored in an information carrier, whichrelative movement comprises at least one curve length defined by thedata, the said data being capable of being corrected in consideration ofthe thickness of the electrode, the width of the operating gap and theerosive condition in the operating gap and being supplied as controlsignals generated in a computing unit by means of aninterpolationprocess to driving members of at least one advancing devicefor at least one of the electrode and the workpiece, characterized by anindexing unit comprising a memory for receiving data stored in theinformation carrier for an angle of rotation, by which angle a system ofcoordinates of the curve length is to be rotated, and a computingcircuit for receiving corrected data of the curve length and the datafor the angle of rotation from the memory, which computing circuitincludes a multiplication circuit and an addition and subtractioncircuit for calculating the new data of the curve length rotated by thesaid angle of rotation and supplying them to a switching circuitarranged downstream thereof, and a return memory for permitting returnof the electrode and workpiece a certain length along the path curve inthe event of undesirable electro-erosion at the operating gap.

2. A circuit according to claim 1 characterized by the fact that theindexing unit is arranged between a correcting computing unit forconverting the characteristic data of the curve length from theinformation carrier in consideration of the diameter of the wireelectrode and the width of the operating gap, and a computer whichgenerates control signals for driving means of advancing devices for theelectrode and the workpiece by means of an interpolation process.

3. A circuit according to claim 1 characterized by the fact that theindexing unit is arranged between a correcting computing unit forconverting the characteristic data of the curve length supplied by theinformation carrier in consideration of the diameter of the wireelectrode and the width of the operating gap, and a conicity computingunit which generates conicity data in consideration of the data relatingto a conicity angle, to the distance between two wire guides arranged ona holding device for the wire electrode and to the distance of one wireguide from the theoretical point of intersection on the face of theworkpiece.

4. A circuit according to claim 1 and further characterized by aswitching unit which receives from the information carrier data foracorrecting computing unit and possibly for a conicity computing unit,for a monitoring device, an erosion generator and for a device for thecontrol of flushing conditions of dielectric medium, which switchingunit is connected to the inlet of the said memory for the transmissionof the data for the angle of rotation.

5. A circuit according to claim 1 characterized by the fact that theinlet of the said memory which receives the data of the angle ofrotation is connected to the outlet of an interpolator, whichinterpolator is arranged downstream of a switching device whichtransmits data for a correcting computing unit, possibly for a conicitycomputing unit, for a monitoring device, for an erosion generator andfor a device for the control of the flushing conditions of thedielectric medium.

6. A circuit according to claim 5 characterized by the fact that thecomputing circuit is provided with three inlets of which the first oneis connected to the outlet of the correcting computing unit forreceiving the corrected data of the curve length supplied by theinformation carrier, the second is connected to the outlet of theswitching device or to the outlet of an interpolator for receiving thedata of the angle of rotation supplied by the information carrier, andthe third is connected to an intermediate memory for receiving the dataof the curve length calculated by the computing circuit for effecting afurther rotation of the same curve length by the same angle.

7. A circuit according to claim 6 characterized by the fact that thefirst and the third inlets of the computing circuit are connected to aninlet of one of the interpolator and the conicity computing unit. 7

8. A circuit according to claim 5 characterized by the fact that thecomputing circuit is provided with two inlets of which the first one isconnected to the outlet of the correcting computing unit for receivingthe corrected data of the curve length while the second is connected toone of the outlet of the switchang device and the outlet of aninterpolator for receiving the data of the angle of rotation supplied bythe information carri- 9. A circuit according to claim 8 characterizedby the fact that the outlet of the correcting computing unit which isconnected to the first inlet of the computing circuit is connected toone of an inlet of the interpolator and the correcting computing unit,the outlet of the computing circuit being directly connected to theother inlet-of the interpolator.

10. A circuit according to claim 1 characterized by the followingcomponents of the computing circuit, input memories for each value ofthe characteristic data of the curve length corrected by the correctingcomputing unit and for the data of the angle of rotation, a selectivecircuit for the selection of the data to be multiplied in themultiplication circuit, a distributing circuit which supplies theresults coming from the multiplication circuit to intermediate memories,intermediate memories for the storage of the results supplied by themultiplication circuit, a further selective circuit for the selection ofthe intermediate results processed in the addition and subtractioncircuit, and a further distributing circuit which supplies the finalresults from the adding and subtraction circuit to two output memories.

11. A circuit according to claim 1 characterized by the fact that amonitoring device is provided which, in the event of changes in theerosive conditions in the operating gap, influences the electricalparameters of the erosion generator, the interpolators and returnmemories associated with the interpolators.

12. A circuit according to claim 1 characterized by the fact that eachinterpolator contains a return memory which memories store thecharacteristic data of the curve length and which are so designed thatthey supply the stored data to the associated interpolator when atrouble signal comes from a monitoring device to generate a controlsignal in inverse order so that the wire electrode returns by the samecurve length.

13. A circuit according to claim 1 characterized by the fact that eachadvancing means consists of a crosstable and that each cross-tablecomprises two moving cross-table

1. A circuit for an electro-eroding machine for the control of therelative movement between at least one electrode and at least oneworkpiece by virtue of data stored in an information carrier, whichrelative movement comprises at least one curve length defined by thedata, the said data being capable of being corrected in consideration ofthe thickness of the electrode, the width of the operating gap and theerosive condition in the operating gap and being supplied as controlsignals generated in a computing unit by means of an interpolationprocess to driving members of at least one advancing device for at leastone of the electrode and the workpiece, characterized by an indexingunit comprising a memory for receiving data stored in the informationcarrier for an angle of rotation, by which angle a system of coordinatesof the curve length is to be rotated, and a computing circuit forreceiving corrected data of the curve length and the data for the angleof rotation from the memory, which computing circuit includes amultiplication circuit and an addition and subtraction circuit forcalculating the new data of the curve length rotated by the said angleof rotation and supplying them to a switching circuit arrangeddownstream thereof, and a return memory for permitting return of theelectrode and workpiece a certain length along the path curve in theevent of undesirable electro-erosion at the operating gap.
 2. A circuitaccording to claim 1 characterized by the fact that the indexing unit isarranged between a correcting computing unit for converting thecharacteristic data of the curve length from the information carrier inconsideration of the diameter of the wire electrode and the width of theoperating gap, and a computer which generates control signals fordriving means of advancing devices for the electrode and the workpieceby means of an interpolation process.
 3. A circuit according to claim 1characterized by the fact that the indexing unit is arranged between acorrecting computing unit for converting the characteristic data of thecurve length supplied by the information carrier in consideration of thediameter of the wire electrode and the width of the operating gap, and aconicity computing unit which generates conicity data in considerationof the data relating to a conicity angle, to the distance between twowire guides arranged on a holding device for the wire electrode and tothe distance of one wire guide from the theoretical point ofintersection on the face of the workpiece.
 4. A circuit according toclaim 1 and further characterized by a switching unit which receivesfrom the information carrier data for a correcting computing unit andpossibly for a conicity computing unit, for a monitoring device, anerosion generator and for a device for the control of flushingconditions of dielectric medium, which switching unit is connected tothe inlet of the said memory for the transmission of the data for theangle of rotation.
 5. A circuit according to claim 1 characterized bythe fact that the inlet of the said memory which receives the data ofthe angle of rotation is connected to the outlet of an interpolator,which interpolator is arranged downstream of a switching device whichtransmits data for a correcting computing unit, possibly for a conicitycOmputing unit, for a monitoring device, for an erosion generator andfor a device for the control of the flushing conditions of thedielectric medium.
 6. A circuit according to claim 5 characterized bythe fact that the computing circuit is provided with three inlets ofwhich the first one is connected to the outlet of the correctingcomputing unit for receiving the corrected data of the curve lengthsupplied by the information carrier, the second is connected to theoutlet of the switching device or to the outlet of an interpolator forreceiving the data of the angle of rotation supplied by the informationcarrier, and the third is connected to an intermediate memory forreceiving the data of the curve length calculated by the computingcircuit for effecting a further rotation of the same curve length by thesame angle.
 7. A circuit according to claim 6 characterized by the factthat the first and the third inlets of the computing circuit areconnected to an inlet of one of the interpolator and the conicitycomputing unit.
 8. A circuit according to claim 5 characterized by thefact that the computing circuit is provided with two inlets of which thefirst one is connected to the outlet of the correcting computing unitfor receiving the corrected data of the curve length while the second isconnected to one of the outlet of the switchang device and the outlet ofan interpolator for receiving the data of the angle of rotation suppliedby the information carrier.
 9. A circuit according to claim 8characterized by the fact that the outlet of the correcting computingunit which is connected to the first inlet of the computing circuit isconnected to one of an inlet of the interpolator and the correctingcomputing unit, the outlet of the computing circuit being directlyconnected to the other inlet of the interpolator.
 10. A circuitaccording to claim 1 characterized by the following components of thecomputing circuit, input memories for each value of the characteristicdata of the curve length corrected by the correcting computing unit andfor the data of the angle of rotation, a selective circuit for theselection of the data to be multiplied in the multiplication circuit, adistributing circuit which supplies the results coming from themultiplication circuit to intermediate memories, intermediate memoriesfor the storage of the results supplied by the multiplication circuit, afurther selective circuit for the selection of the intermediate resultsprocessed in the addition and subtraction circuit, and a furtherdistributing circuit which supplies the final results from the addingand subtraction circuit to two output memories.
 11. A circuit accordingto claim 1 characterized by the fact that a monitoring device isprovided which, in the event of changes in the erosive conditions in theoperating gap, influences the electrical parameters of the erosiongenerator, the interpolators and return memories associated with theinterpolators.
 12. A circuit according to claim 1 characterized by thefact that each interpolator contains a return memory which memoriesstore the characteristic data of the curve length and which are sodesigned that they supply the stored data to the associated interpolatorwhen a trouble signal comes from a monitoring device to generate acontrol signal in inverse order so that the wire electrode returns bythe same curve length.
 13. A circuit according to claim 1 characterizedby the fact that each advancing means consists of a cross-table and thateach cross-table comprises two moving members each displaceable on acoordinate, a wire guide being attached to a moving member of eachcross-table.